In magnetic storage devices a slider is flown over a magnetic disk. The slider contains transducers which write or read the data as the transducer is flown over one of the tracks in the disk.
The flying height of the slider is kept as uniform as possible to minimize read and write errors. Magnetic disks have imperfections. Among the imperfections are variations in the height both along particular tracks and from the inside of the disk to the outside of the disk. In order to maintain a uniform flying height the slider must pitch and roll to accommodate the height variations on the disk. The slider is mounted to an actuator by a gimbal spring or flexure which allows the pitching and rolling motions.
Actuators position sliders over a particular track in one of two ways. Linear actuators move the magnetic head assembly along a radial line from the center of the disk. Rotary actuators swing the magnetic head assembly into position over the track. One advantage a rotary actuator has over a linear actuator is reduced inertia that allows the slider to be positioned over a track more quickly thereby lessening the time necessary to access data. However, the added speed of rotary actuators produces larger accelerations and decelerations as it rotates the slider from position to position. The larger accelerations subject the rotary actuator to larger forces.
Presently, the same flexure used in linear actuators is also used in rotary actuators. Subjecting the same flexure to larger forces produces a problem for rotary actuators. Briefly, the presently used flexure includes a tongue having a gimbal dimple therein. The gimbal dimple is a protrusion extending and contacting the load arm. The gimbal dimple provides a contact point about which the slider can pitch and roll to accomodate variations in the topography of the disk.
The problem with the presently used flexure relates to the radial stiffness or resistance to motion about the radius through which the load arm swings. The radial stiffness is not great enough to prevent the gimbal dimple from sliding to a point on the load arm where the transducer, carried by the slider, is in an off track position where read errors occur. The radial stiffness is also not great enough to overcome the friction force between the load arm and the gimbal dimple when the slider is positioned such that the transducer is off track. Thus, the gimbal dimple slides along the load arm in a radial direction and sticks in an off track position where read errors occur. Hence, the problem is referred to as the stick slip problem.
The flexure presently used is mounted to the load arm in the same manner in both the rotary and the liner actuators. The sliders used are also the same. However, the slider in the rotary actuator is rotated ninety degrees relative to the mounting of the slider to the flexure in the linear actuator. The forces from rotation act along an axis ninety degrees away from the comparable forces in a linear actuator. In addition, these forces are larger due to the quick starts and stops of the rotary actuator. These larger forces combined with switching to a different axis are among the causes of the slip and stick problem. Additional width can be allocated to the track to accommodate the slip and stick problem, however, the data capacity of the disk drops. If the track width is not increased, the number of read errors increases.
Thus, there is a need for a magnetic head assembly for a rotary actuator having a radial stiffness large enough to eliminate the stick slip problem. Rotary actuators could then be used to access data more quickly than linear actuators without increased read errors or sacrificing additional storage space.